1. Field of the Invention
This invention relates to a transparent electromagnetic radiation shield panel, more particularly to a transparent electromagnetic radiation shield panel for placement in front of a TV display device or other such source of electromagnetic radiation to shield the viewer from electromagnetic radiation, and to a method of producing the same. The electromagnetic radiation shield panel according the invention is especially suitable for use with a large plasma display panel.
2. Description of the Background Art
An electromagnetic radiation shield material for placement in front of a display device or other source of electromagnetic radiation is required to have excellent visibility and transparency and a wide viewing angle in addition to excellent electromagnetic radiation shielding capability. Japanese Patent Application Laid-Open No. 5-16281 (JP5-16281) teaches an electromagnetic radiation shield material meeting these requirements.
According to the disclosed invention, a transparent plastic sheet is coated with cellulose acetate propionate to form a hydrophilic transparent resin layer thereon. After being air-dried, the coated sheet is soaked in hydrochloric acid palladium colloid catalyst solution to form electroless plating nuclei in the hydrophilic transparent resin, washed with water and subjected to electroless copper plating. The electroless plating is then patterned by etching by the resist method using ferric chloride. The surface of the electroless plating exhibits metallic luster while the hydrophilic transparent resin layer under the patterned electroless plating exhibits black patterning.
This prior-art invention (JP5-16281), however, requires the hydrophilic transparent resin to be formed with electroless plating nucleus catalyst by soaking in hydrochloric acid palladium colloid catalyst solution before the electroless plating step.
Since electroless plating nuclei are adsorbed on both surfaces of the substrate and both surfaces are plated by this method, however, the plating cost is high. An attempt to reduce the plating cost by plating only the coated surface is ineffective, however, since it requires the opposite surface to be treated to prevent plating, which increases the number of processing steps and increases production cost. Another problem with the method is that the soaking of the substrate in the catalyst solution markedly degrades adhesion between the-coating and the substrate.
Moreover, since the impregnation of the coating with catalyst is effected by soaking the substrate in a catalyst solution, uniform catalyst distribution in the thickness direction of the coating is hard to achieve. The blackening of the coating by plating is therefore difficult to conduct stably and efficiently. The method is also poor in product yield because defects tend to arise during patterning of the plating owing to the unevenness of the plating adhesion.
In addition, the popularity of large television sets with plasma displays has increased rapidly in recent years. When the prior-art electromagnetic radiation shield material is used in panels for the large plasma displays of such TVs, the cutting etc. of panels of different sizes from the material cannot be conducted so as to avoid defective portions since the electromagnetic radiation shielding layer is formed directly on a transparent substrate of a size matched to the plasma display. Therefore, if the panel includes a defect, even though at only one place and no matter how small relative to the total surface area, the whole panel must be discarded as defective. This lowers the product yield.